It’s herobrine…

Unless you have silk touch and can collect grass blocks, what happened here is an Enderman wandered thru the portal carrying a grass block and set it down there. I’ve never seen this before so I’m guessing rare. Is it anywhere near your portal?

ITS THE HEROBRINE

!!!

You found the underground endermen smuggling route. Better run before they catch you!

Either you placed it, or it was maybe an enderman.

That’s an enderman doinga

You must’ve had a wild night to have that thing sitting there. Should’ve marked this nsfw. You silly goose.